Thanks to their lower losses and sharper resonances compared to their metallic counterparts, all-dielectric metasurfaces are attracting a quickly growing research interest. The application of such metasurfaces in the field of refractive index sensing is extremely attractive, especially due to the expected high performance and the simplicity of the sensing element excitation and readout. Herein, we report on an all-dielectric silicon metasurface based on complementary split-ring resonators (CSRRs) optimized for refractive index sensing. A quasi-bound state in the continuum (quasi-BIC) with an ultra-high quality factor can be excited in the near-infrared (NIR) window by violating the structure symmetry. By using the three-dimensional finite element method (3D-FEM), a refractive index sensor for biomedical applications with an ultra-high figure of merit (FoM > 100,000 RIU⁻¹) has been designed, exploiting the quasi-BIC resonance. The proposed design strategy opens new avenues for developing flat biochemical sensors that are accurate and responsive in real time.

In this theoretical study, we explore the enhancement of sensing capabilities in surface acoustic wave (SAW)-based magnetic field sensors through the integration of engineered phononic crystals (PnCs). We particularly focus on amplifying the interaction between the SAW and magnetostrictive materials within the PnC structure. Through comprehensive simulations, we demonstrate the synchronization between the SAWs generated by IDTs and the resonant modes of PnCs, thereby leading to an enhancement in sensitivity. Furthermore, we investigate the ΔE effect, highlighting the sensor’s responsiveness to changes in external magnetic fields, and quantify its magnetic sensitivity through observable changes in the SAW phase velocity leading to phase shifts at the end of the delay line. Notably, our approach yields a magnetic field sensitivity of approximately $S~138\frac{°}{mT}$ for a delay line length of only 77 µm in homogeneous magnetic fields. Our findings underline the potential of PnCs to advance magnetic field sensing. This research offers insights into the integration of engineered materials for improved sensor performance, paving the way for more effective and accurate magnetic field detection solutions.

The study of spin–orbit coupling (SOC) of light is crucial to explore the light–matter interactions in sub‐wavelength structures. By designing a plasmonic lattice with chiral configuration that provides parallel angular momentum and spin components, one can trigger the strength of the SOC phenomena in photonic or plasmonic crystals. Herein, we explore the SOC in a plasmonic crystal, both theoretically and experimentally. Cathodoluminescence (CL) spectroscopy combined with the numerically calculated photonic band structure reveals an energy band splitting that is ascribed to the peculiar spin–orbit interaction of light in the proposed plasmonic crystal. Moreover, we exploit angle‐resolved CL and dark‐field polarimetry to demonstrate circular‐polarization‐dependent scattering of surface plasmon waves interacting with the plasmonic crystal. This further confirms that the scattering direction of a given polarization is determined by the transverse spin angular momentum inherently carried by the SP wave, which is in turn locked to the direction of SP propagation. We further propose an interaction Hamiltonian based on axion electrodynamics that underpins the degeneracy breaking of the surface plasmons due to the spin–orbit interaction of light. Our study gives insight into the design of novel plasmonic devices with polarization‐dependent directionality of the Bloch plasmons. We expect spin–orbit interactions in plasmonics will find much more scientific interests and potential applications with the continuous development of nanofabrication methodologies and uncovering new aspects of spin–orbit interactions.

Taking advantage of highly confined evanescent fields to overcome the free-space diffraction limit, we show plasmonic tweezers enable efficient trapping and manipulation of nanometric particles by low optical powers. In typical plasmonic tweezers, trapping/releasing particles is carried out by turning the laser power on and off, which cannot be achieved quickly and repeatedly during the experiment. We introduce hybrid gold-graphene plasmonic tweezers in which the trap stiffness is varied electrostatically by applying suitable voltages to a graphene layer. We show how the graphene layer absorbs the plasmonic field around the gold nanostructures in particular chemical potentials, allowing us to modulate the plasmonic force components and the trapping potential. We show graphene monolayer (bilayer) with excellent thermal properties enables more efficient heat transfer throughout the plasmonic tweezers, reducing the magnitude of thermophoretic force by about 23 (36) times. This thermophoresis suppression eliminates the risk of photothermal damage to the target sample. Our proposed plasmonic tweezers open up possibilities to develop tunable plasmonic tweezers with high-speed and versatile force-switching functionality and more efficient thermal performance.

The development of high‐sensitivity magnetic field sensors is crucial for precise magnetic field detection. In this context, a theoretical model is presented for a highly sensitive surface acoustic wave (SAW) magnetic field sensor incorporating phononic crystal (PnC) structures composed of Au pillars embedded within a SiO₂ guiding layer. Rectangular and triangular PnC configurations are studied and their potential for improving sensor performance are assessed. In the design, the PnC is integrated into the SiO₂ guiding layer to preserve the continuous magnetostrictive layer, enhancing its interaction with the SAW. Results from the simulations indicate that the proposed sensor can achieve a nearly two orders of magnitude increase in sensitivity compared to a continuous delay line of similar dimensions, and an eightfold improvement over a previous sensor design with PnCs composed of magnetostrictive pillars. This improved performance is attributed to the enhanced interaction between the SAW and the continuous magnetostrictive layer, driven by resonance effects within the PnC. These findings highlight the significant potential of incorporating PnCs into SAW sensors for future high‐performance magnetic field sensing.

In this study, we present a highly-sensitive SAW magnetic field sensor that utilizes phononic crystal structures with Au pillars embedded in a SiO2 guiding layer. The sensor's sensitivity is considerably improved due to increased interactions between the SAW and the magnetostrictive material, facilitated by resonance effects within the PnC structure. Our proposed sensor thus demonstrates significantly enhanced performance compared to sensors with continuous delay lines.